1. FIELD OF THE INVENTION
This invention relates to an image recording apparatus in which a latent image is formed on a photo-sensitive material by optical exposure and is then thermally developed. Thereafter, the photo-sensitive material is piled on an image receiving material so that the image developed on the photo-sensitive material is transferred onto the image receiving material.
2. BACKGROUND OF THE INVENTION
One example of an image recording apparatus of this type has been disclosed in Japanese Patent Application No. 287492/1985 filed by the present inventor. The apparatus uses a photo-sensitive material which is formed by coating a support with at least a photo-sensitive silver halogenide, a reducing agent, a polymerizing compound and a color image forming material. At least, the polymerizing compound and the color image forming material are together contained in microcapsules. A latent image is formed on the photo-sensitive material by optical exposure. In the region of the latent image, the polymerizing compound is polymerized to produce therefrom a macromolecular compound, which thereby hardens the microcapsules. Thereafter, the photo-sensitive material is piled on an image receiving material having an image receiving layer onto which the color image forming material can be transferred. The photo-sensitive material and the image receiving material, which have been piled one on another, are pressed together so that, in the remaining region where the latent image is not present, the microcapsules are at least partially broken to cause the color image forming material to transfer onto the image receiving material. Thereby, the desired image is formed on the image receiving material.
In the thermal developing section of the image recording apparatus, the photo-sensitive material is held between and thereby heated by a heating drum and an endless belt in contact with the cylindrical outer wall of the heating drum. As the photo-sensitive material is heated in the above-described manner, the moisture in the photo-sensitive material is heated and thereby evaporated. The resultant steam is trapped in the photo-sensitive material in such a manner that it is more concentrated where the contact pressure between the endless belt and the photo-sensitive material and that between the photo-sensitive material and the heating drum are lower. That is, the distribution of vapor in the photo-sensitive material becomes non-uniform. As the steam comes out of the photo-sensitive material with the non-uniform distribution of vapor, the photo-sensitive material contracts gradually and differentially, thus being creased.
In the photo-sensitive material, the moisture acts to accelerate developing. Therefore, if water (or steam) is non-uniformly distributed over the surface of the photo-sensitive material, then the image is non-uniformly developed.
The above-described difficulties have been eliminated by an image recording apparatus disclosed in Japanese Patent Application No. 298632/1986 filed by the present inventor. In this apparatus, the photo-sensitive material is preheated before reaching the thermal developing section so that moisture is thereby removed from the photo-sensitive material.
On the other hand, in order that the photo-sensitive material may be processed in its entirety at a constant thermal developing speed, it is preferable that a certain small amount of moisture is uniformly distributed over the photo-sensitive material. However, in the invention of Japanese Patent Application No. 298632/1986, the photo-sensitive material is merely preheated to a certain degree, and it is very difficult to adjust the amount of moisture in the photo-sensitive material.